It is well known that ruminant animals (for example, cattle and sheep) have the unique ability to convert non-protein nitrogen (NPN) to animal protein. This is accomplished, to a large extent, by the action of the microbial flora in the rumen of the animal which degrades such non-protein nitrogen sources to ammonia, which is then converted to protein.
The most widely used non-protein nitrogen source in ruminant feeds has been urea. However there are major problems with the use of urea in ruminant feeds since enzymatic breakdown of urea to ammonia often occurs substantially faster than the microbial uptake of the liberated ammonia. The excess ammonia thus produced can reach toxic levels in the animal which may lead to severe disability or death and such excess ammonia is not utilized for protein synthesis resulting in an inefficient utilization of available nitrogen. Additionally, ruminant animals will noticeably discriminate against urea in feed.
As a result, much work has been done to control the rate at which urea is broken down in the rumen by physically mixing urea with various starch or other polysaccharide sources or molasses, or by combining it chemically with various monosaccharides, polyshaccharides or polysaccharide degradation products to afford slow release urea formulations. See, for example the chapter entitled Nonprotein Nitrogen Supplements for Ruminants in M. Gutcho, "Feeds for Livestock, Poultry and Pets", Noyes Data Corp., (1973), U.S. Pat. Nos. 2,748,001, 3,677,767, 3,873,733 and 3,873,728 and Belgian Pat. No. 806,971.
In the latter two U.S. patents is described the acid catalyzed reaction of urea with partially degraded polysaccharides in the presence of acid (preferably about pH 5-6) to afford an NPN ruminant feed supplement. However, none of the prior art methods describes the preparation of an NPN ruminant feed supplement that can be economically produced on a large scale, competitive with current free urea feed formulations or natural protein feeds such as soybean meal; that contain a relatively high percentage of chemically bound, slowly releasable urea, relative to free urea; and that provide readily available carbohydrates from inexpensive sources.